by Martin Flory
Following a repower and a bottom refit, the 22 m Donzi Wench experienced severe buoyancy problems caused by its wet exhaust system. This well-known 1998 tournament sportfish convertible risked swamping when the vessel was loaded. Called upon to design a solution, the technical experts at Marine Exhaust Systems installed a custom underwater exhaust that now allows Wench to safely run fast and hard.
22 m Donzi Wench
Wench's entire hull bottom had been reengineered and rebuilt to accommodate twin 2,400 hp MTU 16V2000M93 engines, larger props and new fuel tanks. The original wet exhaust system retained so much water in its large tubes that it affected buoyancy after the repower. When Wench was loaded, the cockpit began to flood.
To solve this dangerous issue, Marine Exhaust Systems tackled the challenge of designing a new system for Wench, without sacrificing her 40-knot speed. This demanded that the exhaust be discharged under the boat, while avoiding creating cavitation in the propeller tunnels. An already tight engine room created installation space constraints, as well.
Marine Exhaust Systems' custom solution included dry risers with proprietary hardcoat insulation, and water cans with patented cooling technology. At the system's heart lies a high-performance, ultra-compact bottomless muffler. This versatile and quiet unit, exclusive to Marine Exhaust, is specifically made for underwater applications.
Exhaust discharges out the side of the hull through the company's specially-designed cowling. It's the only unit on the market with laminar flow characteristics, and that eliminates exhaust-related cavitation in tunnel hulls, propellers and water jet intakes.
Installation was performed by Platinum Marine, a full service yacht facility in British Columbia. With the components in place and fitted perfectly to the boat and each other, sea trials on Wench confirmed the new exhaust system's effectiveness. The buoyancy problem was solved, with no loss of speed. Marine Exhaust Systems' custom design also proved to be extremely quiet, while maintaining low temperatures and lower backpressure than the previous system.
More information about Platinum Marine is available here.